Legume fruits contain high levels of proteins, lipids and carbohydrates. Consequently, legume fruits, such as soybeans, and compositions containing legume fruits are considered a great nutrient for human use. Legume fruits also contain compounds that inhibit protease activity. For example, two protein protease inhibitors were isolated from soybeans in the early 1940's, the Kunitz-type trypsin inhibitor (soybean trypsin inhibitor, STI) and the Bowman-Birk protease inhibitor (BBI). See, e.g., Birk, Int. J. Pept. Protein Res. 25:113-131 (1985) and Kennedy, Am. J. Clin. Neutr. 68:1406S-1412S (1998).
STI inhibits the proteolytic activity of trypsin by the formation of a stable stoichiometric complex. See, e.g., Liu, K., Chemistry and Nutritional value of soybean components. In: Soybeans, chemistry, technology and utilization. pp. 32-35 (Aspen publishers, Inc., Gaithersburg, Md., 1999). STI consists of 181 amino acid residues with two disulfide bridges and is roughly spherically shaped. See, e.g., Song et al., J. Mol. Biol. 275:347-63 (1998).
BBI is an 8 k-Da protein that inhibits the proteases trypsin and chymotrypsin at separate reactive sites. See, e.g., Billings et al., Pro. Natl. Acad. Sci. 89:3120-3124 (1992). STI and BBI are found only in the soybean seed, and not in any other part of the plant. See, e.g., Birk, Int. J. Pept. Protein Res. 25:113-131 (1985).
However, due to its natural origin, high levels of microorganisms are carried on the outside of legume fruits, such as soybeans. Consequently, decontamination processes such as heat, organic/aqueous solvent extraction, land high shear purification may be used to reduce such microorganism concentrations to allow it to be safe for human use, e.g., skin care applications. Applicants, however, have found that these processes, which frequently denature the active compounds in the soy, result in a compromised biological efficacy (e.g., a reduction in protease inhibitory activity) which is important for cosmetic and therapeutic uses to the skin, hair, and nails. Furthermore, such processes also can lead to instability of the soy product as well as to an undesirable odor and color generation. Therefore, there is a commercial need to develop a means to reduce the levels of microbials in soy products without compromising the biological benefits of such products.
The object of the present invention is to provide for a soy product (e.g., that can be used as an ingredient in a skin, hair, or nail care composition) that has reduced microbial content but maintains its protease inhibitory activity. Another object of the invention is to provided for a skin, hair, or nail care composition containing such soy product optionally with other active agents.
The present invention relates to legume products containing reduced microbial content that retains legume's beneficial biological activities, processes for obtaining such legume products, and uses thereof in cosmetic compositions.